KR20060069112A - Quality Control Method of Multimedia Broadcasting Using Wireless LAN Multicasting - Google Patents

Abstract

The present invention facilitates the installation of a wireless device by providing a channel automatic selection of an access point and an automatic selection of an access point of a display device when broadcasting the same multimedia source to multiple display devices using a wireless LAN multicast of 802.11 standard. The present invention relates to a method of controlling quality of service of a multimedia broadcast using wireless LAN multicasting to guarantee a quality of service (QoS), and to a display device connected to each access point (AP) in a broadcast server. Requesting delivery of LAN state information; Receiving, by the broadcast server, the packet loss rate by comparing the number of transmission packets transmitted by the broadcast server with the number of received packets transmitted from each display apparatus; Lowering the wireless LAN channel rate of the access point when the packet loss rate is high, and increasing or maintaining the channel rate further when the packet loss rate is low; If the wireless LAN channel speed determined by the above process is more than a predetermined reference speed can be achieved by including the step of transmitting the packet data twice, and if only less than the reference speed to transmit only once.

Description

QUALITY OF SERVICE CONTROL METHOD FOR MULTIMEDIA BROADCASTING USING WIRELESS LAN MULTICASTING}

1 is an exemplary view showing the configuration of a multimedia broadcasting system using wireless LAN multicasting according to the present invention.

2 is a flowchart illustrating a process of automatically selecting a channel having the least radio interference in an access point according to the present invention.

3 is a flowchart illustrating a process of connecting a display device to an access point according to the present invention.

4 is a flowchart illustrating a method for changing a WLAN channel speed and performing retransmission according to the present invention.

* Description of the symbols for the main parts of the drawings *

101: broadcast server 102: access point

103: display device

The present invention relates to a method for controlling quality of service of multimedia broadcasting using wireless LAN multicasting. In particular, when broadcasting the same multimedia source to multiple display apparatuses using wireless LAN multicast of 802.11 standard, automatic selection of a channel of an access point, The present invention relates to a method for controlling quality of service of multimedia broadcasting using wireless LAN multicasting by providing an automatic selection method of an access point of a display device, thereby facilitating installation of a wireless device and ensuring quality of service (QoS).

In general, a wireless LAN is a network environment that provides a LAN service to a wireless terminal such as a PDA or a notebook PC using a wireless LAN card using an access point (AP) device corresponding to a hub of a wired LAN. In the Ethernet system, a wired section between a hub and a user terminal may be considered as a system in which a wireless section between an access point and a network interface card (NIC) such as a wireless LAN card is replaced.

Recently, devices for multimedia broadcasting such as video, sound, and advertisements using wireless LANs have been developed and marketed. In particular, large discount stores, airports, department stores, hotels, and the like, are used to simultaneously broadcast the same advertisement and information images on various displays such as LCD and PDP.

There are various obstacles to lowering the quality of service (QoS) in using the wireless LAN, such as microwave ovens, cordless phones, Bluetooth, obstacles such as walls, distances between communication devices, and other wireless LANs. In order to guarantee the quality of service of wireless multimedia broadcasting from the elements that interfere with the wireless LAN communication, it is conventionally required to reduce the distance between the broadcasting server and the broadcast receiving device or to reduce the influence of obstacles such as walls. Most of the installation was.

However, the above method is limited in the installation location of the devices, there is a problem that a large number of servers must be installed in order to broadcast in a wide place.

In addition, since the conventional multicasting method does not receive an acknowledgment (ACK) for transmission data from the receiving apparatus, the broadcast server does not recognize whether the data is normally transmitted, and thus transmits all the data only once regardless of whether the transmission is successful. There is a problem that the probability of loss is increased.

Accordingly, the present invention has been made to solve the above-mentioned conventional problems. When the same multimedia source is broadcasted to multiple display devices using the 802.11 standard wireless multicast, the channel of the access point is automatically selected and displayed. The purpose of the present invention is to provide a method for controlling quality of service of multimedia broadcasting using wireless LAN multicasting to facilitate the installation of a wireless device and to guarantee the quality of service (QoS) by providing the automatic selection of the access point. have.

In order to achieve the above object, the present invention provides a wireless LAN multimedia broadcasting system including a broadcast server, a plurality of access points, and a display device, and determines whether the channel selection mode of the access point is an automatic mode or a manual mode. Scanning candidate channels when in the selection mode; Selecting a channel having the smallest number of basic service sets (BSSs) among the information obtained by the channel scan, and among them having the smallest RSSI value; When the channel is automatically selected through the above process or the channel selection by the user is completed in the manual selection mode, multicasting data is performed through the channel.

In addition, the present invention includes determining whether the access point selection mode of the display device is an automatic mode or a manual mode, and scanning an access point serving the same broadcast in the automatic selection mode; Selecting an access point having the best RSSI among the information of the access point obtained by the scanning; When the access point is automatically selected through the above process, or when the access point selection by the user is completed in the manual selection mode, displaying the data received through the access point is characterized.

In addition, the present invention comprises the steps of requesting the broadcast server to transmit its own WLAN status information to the display device connected to each access point (AP); Receiving, by the broadcast server, the packet loss rate by comparing the number of transmission packets transmitted by the broadcast server with the number of received packets transmitted from each display apparatus; Lowering the wireless LAN channel rate of the access point when the packet loss rate is high, and increasing or maintaining the channel rate further when the packet loss rate is low; And transmitting the packet data twice when the WLAN channel speed determined by the above process is greater than or equal to a predetermined reference rate, and transmitting only once when the WLAN channel rate is less than the reference rate.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First of all, in adding reference numerals to the components of each drawing, it should be noted that the same components have the same reference numerals as much as possible even if displayed on different drawings.

Also, in the following description, numerous specific details, such as specific processing flows, are set forth in order to provide a more general understanding of the invention, and it is to be understood that the invention may be practiced without these specific details. It will be obvious to them.

In addition, detailed description of well-known functions and structures which are determined to unnecessarily obscure the subject matter of the present invention will be omitted.

1 is an exemplary view showing a configuration of a multimedia broadcasting system using wireless LAN multicasting according to the present invention. As shown in FIG. 1, a broadcasting server 101 for controlling a multimedia broadcasting, and a broadcasting server and an Ethernet are shown. And an access point 102 for transmitting data received from the broadcast server to the display device in a wireless manner, and a display device 103 for reproducing data received through the access point. In this case, since the service area provided by one access point is limited depending on the installation place, a plurality of the access point 102 and the display device 103 are generally installed.                     

In general, since WLANs are heavily affected by performance depending on the degree of interference of each channel, there is a need for a method in which an access point selects a channel having the least interference during initial or operation.

FIG. 2 is a flowchart illustrating a process of automatically selecting a channel having the least radio interference in an access point according to the present invention. As shown in FIG. 2, when the access point automatically selects a channel, the channel is selected by a channel scan. do.

That is, the information obtained when the access point (AP) scans a channel during an initial or active operation includes BSS (Basic Service Set), 802.11 mode (a / b / g), and RSSI (Received Signal Strength) of each channel. Indication) etc., when the AP selects a channel, it selects the smallest number of BSSs among the candidate channels, and the smallest RSSI value among them.

For reference, when there is a channel having the same number of BSSs in an 802.11 b / g AP, a channel having a low speed of a slow 802.11b BSS is selected, and each AP may reselect a channel at the request of a broadcast server even during operation.

When the channel is automatically selected as described above or manually selected by the user, the access point multicasts data through the set channel unless the channel is reset.

As described above, the method for selecting a channel for multicast in the access point has been described. Hereinafter, when there are several access points serving the same broadcast, a method for determining which access point the display device connects to and receives a broadcast service from Explain.

3 is a flowchart illustrating a process in which a display device connects to an access point according to the present invention, and when the access point is automatically selected as shown in FIG. Selecting a good access point, each display device can reselect the access point even during operation at the request of the broadcast server.

When the access point is automatically selected as described above or when the access point is manually selected by the user, the display apparatus displays data received through the selected access point unless the access point is reselected.

As described above with reference to Figs. 2 and 3, the present invention expands the service area of the access point by selecting an optimal channel in the access point and selecting an optimum access point in the display apparatus, thereby reducing the number of access points. To broadcast a large area.

On the other hand, the existing wireless LAN multicasting transmits at a fixed channel rate, but because the ACK is not received from the receiving device, retransmission is not performed even when a transmission error occurs. There is a falling problem. Accordingly, the present invention provides a method for performing WLAN channel speed change and retransmission to ensure the quality of a broadcast service.

4 is a flowchart illustrating a method for changing a wireless LAN channel speed and performing retransmission according to the present invention. First, a broadcast server determines a wireless LAN channel rate and a number of data transmissions. A request is made to transmit its WLAN status information to a display device connected to the AP). In this case, the state information delivered to the broadcast server by the display device is the number of received packets, RSSI, and the like.

The broadcast server, which has received the wireless LAN state information from each display device in response to the request, compares the number of transmission packets transmitted by itself with the number of received packets received from each display device, and determines how many packets are lost. If a lot of loss occurs, lower the WLAN channel speed of the access point, and if there is no packet loss, increase the channel speed more or maintain the current state.

Next, if the WLAN channel speed determined by the broadcasting server is 24Mbps or more, there is a margin of wireless bandwidth. Therefore, the data transmission frequency is set to transmit twice to prevent packet loss. Of course, the criterion of twice transmission of the packet may vary according to the type and compression rate of the multimedia transmitted by the 24Mbps broadcast server.

If a lot of packet loss occurs in the display device even if the WLAN channel speed is lowered, or if the channel speed is set to be insufficient for processing broadcast data to be transmitted, the broadcast server sends a command to the access point to reselect the WLAN channel. In addition, each display device may be reconnected to an access point having the highest RSSI to improve the packet reception rate to ensure the quality of service set by the broadcast server.

 As described above, the present invention provides a method for controlling quality of service of multimedia broadcasting using wireless LAN multicasting, when the same multimedia source is broadcasted to multiple display devices using wireless LAN multicast of 802.11 standard. By providing a technology for automatically selecting an access point of a display device, there is an effect of facilitating installation of a wireless device and ensuring quality of service (QoS).

Claims (10)

In a wireless LAN multimedia broadcasting system consisting of a broadcast server, a plurality of access points and a display device, Determining whether the channel selection mode of the access point is an automatic mode or a manual mode, and scanning candidate channels in the automatic selection mode; Selecting a channel having the least number of basic service sets (BSSs) among the information obtained by the channel scan, and among them having the smallest RSSI value; When the channel is automatically selected through the above process, or when the channel selection by the user in the manual selection mode is completed, multicasting data through the channel, characterized in that the multimedia using the wireless LAN multicasting Method of controlling the quality of service of broadcasting. The wireless LAN multicasting of claim 1, wherein the information obtained during the channel scan includes BSS information, 802.11 mode (a / b / g) information, and Received Signal Strength Indication (RSSI) information of each channel. Quality of service control method using multimedia broadcasting. The method of claim 1 or 2, wherein in the 802.11 (b / g) access point (AP), if there are channels having the same number of BSSs, the slower 802.11b BSS channel is selected to select a channel. Quality of service control method of multimedia broadcasting using WLAN multicasting. The method of claim 1, wherein the access point is configured to reselect a channel at the request of a broadcast server even during operation. In a wireless LAN multimedia broadcasting system consisting of a broadcast server, a plurality of access points and a display device, Determining whether the access point selection mode of the display device is an automatic mode or a manual mode, and scanning an access point serving the same broadcast in the automatic selection mode; Selecting an access point having the best RSSI among the information of the access point obtained by the scanning; When the access point is automatically selected through the above process, or when the access point selection by the user in the manual selection mode is completed, displaying the data received through the access point multi-LAN Quality Control Method of Multimedia Broadcasting Using Casting. The method of claim 5, wherein the access point is reselected at the request of a broadcasting server even during the operation of the display device. 7. In a wireless LAN multimedia broadcasting system consisting of a broadcast server, a plurality of access points and a display device, Requesting, by the broadcast server, to transmit its WLAN status information to a display device connected to each access point (AP); Receiving, by the broadcast server, the packet loss rate by comparing the number of transmission packets transmitted by the broadcast server with the number of received packets transmitted from each display apparatus; Lowering the wireless LAN channel rate of the access point when the packet loss rate is high, and increasing or maintaining the channel rate further when the packet loss rate is low; If the wireless LAN channel speed determined by the above process is a predetermined reference speed or more, and transmits the packet data twice, and if less than the reference speed, including the step of controlling to transmit using a wireless LAN multicasting, characterized in that made Method of controlling quality of service of multimedia broadcasting. The method of claim 7, wherein the state information delivered by the display device to the broadcast server includes received packet number information and RSSI information. 8. The broadcast server of claim 7, wherein, even if the WLAN channel speed is lowered, if a packet loss occurs in the display device or if the channel speed is set to be insufficient for processing the broadcast data to be transmitted, the broadcast server transmits the WLAN channel to the access point and the display device. And reselecting the access point. 8. The method of claim 7, wherein the channel reference rate for determining the number of times of packet data retransmission is 24 Mbps.

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